Marl

Marl is a naturally occurring alluvial clay or deposit that contains a relatively large amount of calcium carbonate. It was spread on fields to counteract acidic soils, and to improve the water retention of sandy soils, a process known as marling. It was also spread on reclaimed mosslands such as Chat MossLarge area of peat bog that makes up 30 per cent of the City of Salford, in Greater Manchester, England, to prevent them from shrinking.^[1]

The term has been loosely applied to a variety of earthy deposits, the chief constituents of which are an intimate mixture of clay and calcium carbonate formed under freshwater conditions; these typically contain 35–65% clay and 65–35% calcium carbonate.^[2][3][4]

See also

• Keuper MarlNow deprecated term for multiple layers of mudstone and siltstone that occur beneath parts of the English Midlands and beyond.